:salam2:
This year I went to KSA and when I reached the city of Madina Munawara, I decided to visit the so called place which is known as ‘Valley of Jinn’, located some 20 km away from the city to see the Jinn 
We asked many local residents whereabouts of this valley but surprisingly no one know about ‘Jinn valley’ or ‘Wadi Al Jinn’. Then we came to know that this valley is actually called ‘Mantaza Al Baida’ which means “Al-Baida (white) Park”. It is indeed a beautiful picnic spot.
Anyhow, when we reached there I parked my car to see if it goes in opposite direction (upwards) or not, as seen in many videos on youtube etc., that the car, water or empty bottle move in opposite direction (upwards).
Well, first of all the slope of the road towards “Al-Baida Park” as known as “wadi Al Jinn” is constantly upwards but the road look like a straight road. However, when we see RPM gauge, its little bit increased due to load (by driving upwards). So the road is not straight but in slope which is constantly going upwards.
Secondly, my car didn’t went in opposite direction (upwards) but it went in downward direction due to the flow of air pressure. Even if there is no air (wind) then due to shape of the earth it goes downwards (see this video http://www.paklinks.com/gs/video-gallery/655345-explanation-similar-to-valley-of-jinn.html)
Thirdly, I asked the local residents in that area why their parked cars are not moved by the Jinn? Why Jinn only moves or pushes cars of the visitors? Obviously the answer is that ‘there is no Jinn’
Fourthly, local taxi charge Saudi Riyals 100 - 150 (US$ 40) and buses 40 (US$ 11) each person for the tour and the rate increase during the season, so this is another way of earning money by the taxi/bus drivers.
Fifthly, some people now give importance to this valley by relating an incident of Prophet Muhammad 
the He stayed there and there was a well which water taste sour but it is now sweet because of His visit, or something like that. I couldn’t find/saw any well nearby this area 
Last but not least, Saudi local papers Akaz and Al Shamas including MBC Arabia posted an article on “Wadi Al Jinn”, after consulting with local authorities that there is no religiously or historically importance ever mentioned in any religious or historical books, neither there are any Jinns.
